Liquid sloshing in Floating LNG tank could potentially cause strength issue, resonant vibration and fatigue damage of the tank structures. An FSI approach is used in this paper to provide solutions in both fluid domain and structural domain. The dynamic stresses from the solutions can be used to potentially address the three critical issues in floating LNG tank design. The first one is the strength of the tank structure under the peak impact loads. The second one is the resonant vibration when the excitation from the ship motion is near the natural frequencies of the LNG tank. The third one is the tank structure fatigue under dynamic loads that is caused by liquid sloshing due to ship motions even in the normal operation.

In this paper, an FSI approach is used for modeling liquid sloshing induced by vessel motion in a FLNG tank. The scaling law [1] is used in the simulation to reduce the size of the model. Transient Computational Fluid Dynamics (CFD) is coupled with transient Computational Structural Dynamics (CSD). The gas and liquid inside tank are modelled with Volume of Fluid (VOF) theory. The FSI modeling can be potentially used to assess strength, vibration and fatigue in FLNG tanks due to liquid sloshing. The FSI results show vessel motions significantly affect impact pressure and dynamic stress on the tank. FSI can capture coupled physics of vessel motions, sloshing, impact pressure, and dynamic stress on the tank.

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